Cardio seems to burn more calories, however, strength training keep your metabolism active for a longer period and thus you lose even when you are resting. Regular repetitive cardio may lead to injury as recovery is important for cardio exercises. Strength training is sustainable way of reducing body fat and it also increase lean muscle which are lost in cardio sessions. 

A best diet is customized according to your present body structure and its subsequent needs. Not one diet fits all. And diet also depend on your expectations. A good diet is composed of all the essential items like protein, fats, carbs, vitamins, trace minerals, etc. which are important for life processes. The right amount in which all of these should be administered is variable from person to person. 

You don’t need to count calories like maniacs. Just take care of portions and do not overdo any particular food. Your calorie intake depends on your daily activity. An active individual can take more calories than a sedentary person. Just make sure that calories should not be way too much less than daily requirement as it will hamper other biochemical processes. 

Grains are not essential and you can take similar nutrients from other sources as well. Try to eat more of whole grains as they are rich in dietary fiber. 

Yoga works on your internal organs and helps detox the body from within. This leads to a feeling of balance, inner fulfilment, and mental relaxation. Gym sessions focus on boosting your cardiovascular health and toning, without any focus on the aspect of mental health. However, any form of exercise do secrete endorphins (happy hormones) which help in elevating mood and make sure that depression and stress are at a distance.